We’ve established that Dunkin Donuts signs in the distance are better than mirages in the desert, but sometimes may still be made up. So here’s something else I noticed driving on the highway: cars travel in packs.

It’s not noticeable until you blink those hazards and pull off and stop on the shoulder for a while. Cars drive by in packs of 4-5. There are still a few hundred feet between the cars in a pack, but there is a gap significantly longer than few hundred feet in between packs.  Each pack takes about 10, 20 seconds to pass by, followed by some 30-60 seconds of nothing before another pack comes along.

Isn’t it strange that random stranger cars would end up packed up like that driving down the highway? Why wouldn’t they be evenly spaced out? Why are there distinct packs?

I feel like there should be some kind of theory describing this phenomenon, or maybe this is a manifestation of something else well-studied that’s already been observed elsewhere. Like maybe why cherries come in bunches of twos. Or why fish organize themselves into schools. But schools of fish has a purpose, and it doesn’t seem like schools of cars would really have a purpose on the highway. Except maybe to avoid speeding tickets. Just kidding. I don’t think ticket-avoidance is strong enough of a common goal to unite packs of cars together. Or maybe it is …

Anyways, google google google later … I didn’t really get anywhere, but it does seem like people tend to model traffic like a fluid flow (and also people write whole PhD dissertations on this stuff). Now, I’m no mechanical engineer; I know nothing about fluid flow … but maybe fluids also tend to flow in clumps. I’ll ask my MechE friends.